The evolution of the telecommunications in general and of the packet switching networks in particular is driven by many factors among which two are worth emphasizing: technologies and applications.
Communication technologies have realized these last years considerable progress with:
the maturing of new transmission media and specially of optical fiber. High speed rates can now be sustained with very low bit error rates. For example, the very important bandwidth provided by optical connections, their low attenuation and their high transmission quality are turned into profit for long distance networks as well as for high rate local networks. PA1 the universal use of digital technologies within private and public telecommunications networks. PA1 Improving old applications. Sub-second response times, which are achievable on low cost personal computers, have raised user expectations so that the lengthy wide area networks response times that were acceptable some years ago are today no longer tolerable. The user interface can be bettered, for example, with fast response full screen applications. PA1 Optimizing communication networks. There is a need for rationalizing the many disparate networks that major users have. Investments can be optimized by integrating heterogeneous traffics like voice, video, and data over the same transport facilities regardless of protocols. Users want the opportunity to control their networking cost by choosing among the different price/performance options offered by the variety of vendors and carriers and to maximize their ability to take advantage of applications built on top of disparate underlying network technologies. However, the motivation for rationalization is not only to save money on links but also to provide a better networking service by integrating the many disparate networks into a single coherently managed unit. PA1 Doing new applications. Emerging applications like graphic, image, video, and multimedia processing are requiring a very large volume of traffic. These new applications that were not feasible (or even thinkable) before are now accessible and generating an ever-increasing demand on bandwidth. PA1 a very large flexibility to support a wide range of connectivity options, PA1 a very high throughput and a very short packet processing time, PA1 an efficient flow and congestion control. PA1 the flow control for regulating the emitting data rate of the calling subscriber at a rate compatible with what the receiver can absorb. PA1 the load regulation for globally limiting the number of packets present in the network to avoid an overloading of the resources, and PA1 the load balancing for fairly distributing the traffic over all the links of the network to avoid a local congestion in particular resources. PA1 each adapter being connected to a network high speed transmission line or trunk, the transmission bandwidth of which is shared by several connections, each connection establishing a path between a source and a destination, through an assigned buffering queue means controlled by processor means including means assigned line and network managements, said method including: PA1 monitoring each transmit queue data level and output activity with respect to references dynamically defined or preassigned to the considered queue by said line resources management facilities and in case of detecting a predefined error event, then, PA1 temporarily barring input to the considered transmit queue; and, PA1 reporting said event to line and network managements for final decision on said queue traffic.
The emergence of high speed transmission entails an explosion in the high bandwidth connectivity. The advent of these new technologies has pushed the speed of communication links to the area of the giga-bit per second representing an increase of several orders of magnitude over typical links in traditional networks. The increase of the communication capacity is generating more attractive tariffs and large bandwidths are economically more and more attractive.
On the other hand, in relation with these new emerging technologies, many potential applications that were not possible before are now becoming accessible and attractive. In this environment, three generic requirements are expressed by the users:
Data transmission is now evolving with a specific focus on applications and by integrating a fundamental shift in the customer traffic profile. Driven by the growth of workstations, the local area networks interconnection, the distributed processing between workstations and super computers, the new applications and the integration of various and often conflicting structures--hierarchical versus peer to peer, wide versus local area networks, voice versus data--the data profile has become more bandwidth consuming, bursting, non-deterministic, and requires more connectivity.
Based on the above, there is strong requirement for supporting distributed computing applications across high speed networks that can carry local area network communications, voice, video, and traffic among channel attached hosts, business engineering workstations, terminals, and small to intermediate file servers.
This vision of a high speed multiprotocol network is the driver for the emergence of fast packet switching networks architectures in which data, voice, and video information is digitally encoded, chopped into small packets and transmitted through a common set of nodes and links. This high speed packet switching network includes nodes interconnecting high speed links (lines or trunks) for orienting the traffics of a great number of users toward preassigned paths each establishing a connection between two end users. Given the high bandwidth over said links, hundreds of connections are supported by each link, and thus handled in each network node. One may therefore easily imagine how catastrophic the consequences of any transmission error that would jam the network, and possibly put the whole system down, would be. This certainly does emphasize the importance of early detecting these errors, particularly when they are of a transient nature, and reorganizing the network traffic accordingly. The present invention shall focus on that.
An efficient transport of mixed traffic streams on very high speed line means for these new network architectures, a set of requirements in terms of performance and resource consumption which can be summarized as follows:
In high speed networks, the nodes must provide a total connectivity. This includes attachment of the user's devices, regardless of vendor or protocol, and the ability to have the end user communicate with any other device. The network must support any type of traffic including data, voice, video, fax, graphic or image. The nodes must be able to take advantage of all common carrier facilities and to be adaptable to a plurality of protocols. All needed conversions must be automatic and transparent to the end user.
One of the key requirements of high speed packet switching networks is to reduce the end-to-end delay in order to satisfy real time delivery constraints and to achieve the necessary highnodal throughput for the transport of voice and video.
Increases in link speeds have not been matched by proportionate increases in the processing speeds of communication nodes and the fundamental challenge for high speed networks is to minimize the packet processing time within each node. In order to minimize the processing time and to take full advantage of the high speed/low error rate technologies, most of the transport and control functions provided by the new high bandwidth network architectures are performed on an end-to-end basis. The flow control and particularly the path selection and bandwidth management processes are managed by the access points of the network which reduces both the awareness and the function of the intermediate nodes.
Communication networks have at their disposal limited resources to ensure an efficient packets transmission. An efficient bandwidth management is essential to take full advantage of a high speed network. While transmission costs per byte continue to drop year after year, transmission costs are likely to continue to represent the major expense of operating future telecommunication networks as the demand for bandwidth increases.
Thus considerable efforts have been spent on designing flow and congestion control processes, bandwidth reservation mechanisms, routing algorithms to manage the network bandwidth.
An ideal network should be able to transmit a useful traffic directly proportional to the traffic offered to the network and this as far as the maximum transmission capacity is reached. Beyond this limit, the network should operate at its maximum capacity whatever the demand is. In the reality, the operations diverge from the ideal for a certain number of reasons which are all related to the inefficient allocation of ressources in overloaded environment.
For the operating to be satisfactory, the network must be implemented so as to avoid congestion.
The simplest solution obviously consists in oversizing the equipments so as to be positioned in an operating zone which is distant from the congestion. This solution is generally not adopted for evident reasons of costs and it is necessary to apply a certain number of preventive measures among which the main ones are:
The flow and congestion control operations in the network generate additional traffic on the network. Ideally only the exact bandwidth needed at any time by a network connection should be dynamically reserved for that connection, and also only the exact bandwidth needed for the network control operations should be reserved for that purpose.
However, it is essential for an efficient flow and congestion control to provide at any time enough network resources in terms of bandwidth or performance to the control traffic. The control traffic can be divided into two main families including a network routing control traffic, and a network signalling control traffic.
The routing control traffic is used for distributing the network topology information between nodes of the network. This information is necessary mainly for the computation of routing paths between nodes in the network. Routing control messages are generally broadcasted to all nodes by means of Spanning Tree or flooding mechanisms.
Insufficient resources for routing control messages could lead to invalid network topology tables. It is obvious that a node, with an erroneous or obsolete view of the network topology, may take wrong routing decisions.
The signalling control traffic is used to establish point-to-point and point-to-multipoint network connections across the network. Signalling control messages are generally forwarded towards the different nodes along the path of the connections. Insufficient resources for signalling control messages could typically lead to errors or at least to a degradation of the quality of service in the establishment and management of network connections.
Because of the high importance of the network control traffic, enough bandwidth on the links must be reserved to transmit the routing and signalling control messages throughout the network, between sources and destinations. The fraction of the total link bandwidth specially reserved for the control traffic is, in most broadband network architectures known today, a fixed percentage (e.g. =15%) of the links bandwidth.
As already mentioned, errors in the network operation are very detrimental. Some of these errors are so-called solid errors, others are transient errors.
Means are already known for taking care of solid errors. Transient errors, on the other hand are very tricky because, by definition, the error origin may disappear and yet its consequences may be catastrophic for the whole high speed network operation if not rapidly detected and taken care of. As shall be apparent from the following description of a preferred embodiment of this invention, a transient error may lead to the network full congestion and break-down.
Accordingly whatever be the type of error it could be detrimental to the whole network operation when it is not taken care of rapidly. This is particularly true for so-called transient errors affecting, for instance clock signals. Given the present architecture of available data communication networks, this kind of error may remain undetected, leading to data enqueuing overflow, new errors being generated, congestion occuring and finally possibly freezing the whole data network operation.
The present invention shall focus on monitoring, detecting and processing said transient errors early enough to avoid network congestion.